Criteria for the credit deduction from the free 500 hours

I am using a MySQL service from Railway in a flask application deployed on the web using Render. I was wondering if I would be charged even when no one is using my application.

Also, if I am continuously charged, is there a way to stop the service temporarily when my application hasn't been accessed for a long time and then reboot it again when someone tries to access it?

N/A

this is currently not supported by railway, you'd need to delete your service if you didn't want to be charged for it.